What is BS 6740 - Departures from roundness about?
BS 6740 specifies a method for determining departures from roundness by measuring variations in radius by means of contact (stylus) instruments.
BS 6740 applies to the assessment of the departures from ideal roundness of a workpiece through the medium of a profile transformation, obtained under reference conditions, expressed with respect to any one of the following centres:
- Centre of the least squares circle
- Centre of the minimum zone circle
- Centre of the minimum circumscribed circle
- Centre of the maximum inscribed circle
Each of these centres have its own application.
BS 6740 deals with the departures from the roundness of the measured profile, procedure, calibration, and determination of systematic errors of rotation. BS 6740 gives rules for plotting and reading polar graphs.
Who is BS 6740 - Departures from roundness for?
BS 6740 on departures from roundness is useful for:
- Manufacturers of stylus instruments
- Designers of stylus instruments
- Civil engineers
- Product development teams
- Testing authorities
- Quality assurance personnel
Why should you use BS 6740 - Departures from roundness?
Stylus instruments are widely used for measuring the finishing of the surface. There are various types of stylus instruments depending upon their applications.
BS 6740 lays down the technicalities for a method to determine the departures from roundness with the help of different types of stylus instruments.
BS 6740 establishes:
- Types of instruments and general requirements
- Recommendations for the use of instruments
- Procedures for calibration of instruments and verification of their characteristics
BS 6740 also provides you with the surface characteristics and dimensions of stylus instruments as well as covers instruments errors.
BS 6740 assists with the departure from the roundness of the measured profile of the workpiece. BS 6740 helps in determining the systematic errors of rotation. BS 6740 aids with the rules for plotting and reading polar graphs.
BS 6740 provides guidance on the method for determining departures from roundness by measuring variations in radius which is very helpful for the users of stylus instruments. 
